Interest in the use of solution inhalers and dry powder inhalers (DPIs) has increased in recent years, broadening from systems for the delivery of traditional respiratory medications to the delivery of inhaled proteins, peptides, and analgesics. This has led to numerous developments and a range of inhaler designs and technology, each with advantages and distinctive features. Novel devices for aerosolization of solutions can be broadly divided into three main classes: adaptive aerosol delivery devices, metered dose liquid inhalers (MDLIs), and breath-actuated nebulizers. Similarly, the wide range of DPIs in development can be classified generally according to their means of storing and providing the drug, that is, as single capsules, a bulk reservoir, or multiunit-dose devices. Choice of a system for delivering a liquid solution is based on a number of factors (e.g., ease of use, convenience, aerosol properties, dose delivery, and drug deposition), the combination of which will have an impact on the single most important factor: clinical benefit. Ultimately, the patient must be able to use the device easily, maintain it, and derive clinical benefit from the drug delivered by the system. Physicians and patients must recognize that if one system does not work, an alternative must be tried.